Rare charm decays can be investigated by the modern experiments, due to
the high luminosity and precision achieved. The different experimental
scenarios allow those studies in \(e^+-e^-\)  (BESIII [1]}, CLEO-c [2]}, BELLE [3]}, BELLE2 [4]},
and BABAR [5]}) and \(p-p\)  (LHCb [6]}, CDF [7]}, and D0 [8]}) collisions. The first scenario is
carachterized by extremely clean environments, in some cases the double-tag
technique allows almost background free studies, quantum coherence, high
trigger efficiency, and easy detection of neutral particles. On the other
side, the latter scenario offers large production rate, and excellent time
resolution.
